LINKEAN SOCIETY OF LONDON. 3J 



Society, two j-ears ago, with great fulness and clearness by Messrs. 

 Arber and Parkin, in tlieir paper on the 'Origin of Angiosperins'*. 

 Tbey sbowed in detail tbat, if tbe Angiospermous flower was 

 derived, as they hold, from a source allied to the Bennettitea), its 

 evolution, as suggested by Wieland, must have been essentially a 

 process of reduction. I am in general agreement with the views 

 of these authors, and only wish to point out that they are nob 

 inconsistent with the great relative antiquity of simple and, ex 

 hypoihesi, reduced forms, for which in the case of the Amentiferoe 

 there seems to be good geological evidence. Eeduction appears 

 to have often been a rapid, indeed a comparatively sudden change 

 as shown by the frequent occurrence of much simplitied foi-ms in 

 the same family in which the prevailing structure is typically com- 

 plete. I need only instance certain Poterieae among the Rosaceae, 

 Senehiera among the Cruciferse, Peplis among the Lythraceae, 

 Garrya, with its catkin-like inflorescence, and pei'haps Davidia 

 among the Cornaceae, but similar cases are exceedingly common. 

 It thus appears quite probable that some groups with very simple 

 flowers, though not " primitive " may be very ancient, tracing 

 their origin from forms which in quite early days underwent 

 reduction from the highly developed flowers which probably 

 characterized the first autonomous Angiosperms. 



The tentative and somewhat fragmentary observations which I 

 have brought before you this afternoon tend to the following 

 conclusions : — 



1. That at all known stages of the past history of plants there 



has been a thoroughly eflicient degree of adaptation to the 

 conditions existing at each period. 



2. That, the characters of plants having always been as highly 



adaptive as they now are, Natural Selection appears to afford 

 the only key to evolution which we at present possess, for 

 all periods covered by the palseontologieal record. 



3. That this record only reveals a relatively short section of 



the whole evolution of plants, during which, though there 

 has been considerable change, there has not been, on the 

 whole, any very marked advance in organization, except 

 in cases where the conditions have become more complex, 

 as shown especially in the floral adaptations of Angio- 

 sperms. 



4. That simple forms existing at the present day are, as a rule, 



of a reduced rather than a primitive nature, but that such 

 reduction may have often set in at a relatively early stage 

 of evolution, and is therefore consistent with a considerable 

 degree of antiquity in the reduced forms. 



* Journal of the Liunean Society, Botany, vol. xxxyiii. (1907) p. 29. 



